The present invention relates to separating meat components such as fat and lean meat generally, and more particularly to upgrading trim pieces of meat to a fraction having a higher lean meat content and a fraction having a higher fat content.
Various techniques have been disclosed for dividing fat and lean meat using photoelectric or color sensitive detectors. These techniques are representative of efforts to eliminate problems associated with manual separation of fat and lean portions of meat products. One such technique is disclosed in U.S. Pat. No. 3,930,991 to Gillespie. In Gillespie, a combination of lean and fat meat is first cut into chunks of uniform size and then passed through a photometric sensor for detecting an optical property relating to the lean meat content of the chunks. The chunks are then sorted by a device responsively coupled with the photometric sensor. The individual chunks are preferably maintained at a low temperature close to freezing (which, for meat, is about 26.degree.-32.degree. F.) in order to permit singularizing of the chunks for passage through the photometric sensor. Such requirements significantly reduce the rate of separation in addition to increasing operating costs for the process as discussed in U.S. Pat. No. 4,201,302. Further, it has been observed that meat ground at a temperature below about 40.degree. F. undergoes "fracture" which is due in part to the presence of frozen crystals in the meat at this temperature. This reduces the binding qualities of the meat, as well as the quality of protein in the meat. When meat having reduced binding qualities is used to make bologna or sausage, for example, the end product has an undesirable texture and can fall apart. It has also been observed that product formed by grinding semifrozen or frozen meat has less distinctive color characteristics than if it were ground from nonfrozen meat (i.e., the red lean portions become lighter in color). Accordingly, detection of lean and fat based on color or light-dark characteristics of the meat product with conventional optical sensing devices becomes more difficult. Meat product that is ground when frozen also has a spongy texture which includes pores that can appear as dark spots to the detection apparatus. An erroneous lean meat reading can result.
U.S. Pat. No. 2,373,361 to Walter also discloses a system using photoelectric detectors for separating fat and lean portions of meat products. In this system, substantial processing is required to condition the individual particles for passage through the photoelectric sensor. Specifically, the fat trimmings are ground up and deposited on a belt. The ground meat is pressed into a thin layer on the belt and then cut into thin ribbons of about 1/2 to 1 inch in thickness. Light reflected from the ribbons is sensed by a photoelectric cell. Scrapers are operated in accordance with the light detected from the photoelectric cell to scrape lean meat from the belt into a first chute. The fatter portions remain on the belt and are later scraped therefrom into a second chute. The process depends on the grinding of the meat into course particles so that it can be flattened onto the belt and also depends on the stickiness of the meat to adhere to the belt.
U.S. Pat. No. 4,201,302 to Roth discloses separating fat and lean meat by passing the combined fat and lean meat through an extruder sized to form a plurality of generally continuous chains of material. A sensor senses the character of the material along the length of each chain while the meat product material is passed through a tube. A diverter operates in response to the sensor to direct fat exiting the tube toward one collection bin and lean meat exiting the tube toward another collection bin. It has been found that the inner walls of the tubes can become contaminated with lean or fat particles (the meat product material smears on the inner walls of the tubes) which can lead to sensing errors. In addition, the tubing can become fogged over time which can result in erroneous fat readings by the sensing apparatus. Accordingly, the tubes must be continuously cleaned and possibly replaced to maintain sensing accuracies. The complex cutting arrangement for directing the fat and lean portions to the appropriate bin also must be maintained to provide accurate removal of material. It has also been observed that the meat product flow rate from the grinder can vary, thereby interfering with the timing of the diverter or cutting devices.